As others have said, you can't duplicate results day after day, even with the same food and the same insulin. If you are within 2mmols of the previous day's result, that is a reasonable outcome.
Don't worry yourself about insulin resistance. It is not something you need to consider at this stage, if at all, unless you get significantly overweight and your insulin needs become very high... and I am talking about 15-20 units for every meal and 50+ units of basal. Any increase in insulin needs for you, particularly at the moment, is much more likely to be due to your beta cells dying off, so just accept that you will gradually need to increase your insulin doses during the honeymoon period although some people find they need to reduce them first and then increase them. It really is not something that you should concern yourself with at all, so please put it out of your head. You need however much insulin you need and it will change over time, sometimes up and sometimes down and you just have to learn to go with the flow.
Can you just remind us how long you have been diagnosed and been on insulin. I am wondering if you are just trying to do too much too soon. I know the feeling because I was really chomping at the bit to get it right straight away but it's like expecting to go and play in the Wimbledon final against Serena Williams when you normally play club level once a week. You have to set yourself reasonable expectations. It takes time and experience and practice and knowledge and you don't get that overnight. Be patient with yourself until things slowly click into place both with you getting the hang of it but also your body slowly stabilizing, because the honeymoon period can be pretty challenging.
One thing I do which helps with the timing of insulin and meals is to watch my Libre and not eat until I see the insulin starting to kick in and drop my levels. I have a rule were I don't eat if my levels are above 8 unless I really can't help it. So I inject for my food and then I keep a close eye on my Libre until I see my levels start to drop. Generally I like to be mid 5s when I eat but I would aim for mid 6s for yourself and that should still give you plenty of time for whatever you eat to hit your blood stream. So, if your levels are 8.5 when you inject for lunch, wait until they reach 6.5 before you start eating. If my levels are above 10 I can be waiting 2 hours to eat sometimes because high BG levels cause temporary insulin resistance. I know it isn't possible for everyone to wait 2 hours to eat a meal, but once you start keeping your levels mostly in range it becomes less of an issue.
I would also like to say that I learned almost everything I know from this forum and experimenting on myself, so don't expect too much from your clinic staff. As
@Inka said, they can only ever make a best guess, so ultimately you need to learn how your particular body works in any given set of circumstances and adjust things accordingly. Gradually it takes up less head space and becomes more intuitive and I see it as more of a challenge and a game now rather than a serious health issue. Libre takes a lot of the strain out of managing my diabetes compared to finger pricking, but I wonder at this stage if it is giving you too much info and you seem to be applying Type 2 mentality to your results. If you were only finger pricking before your next meal, you would not know what your levels were 2 hours after your meal and therefore not be getting frustrated about them. If you were high at your next meal then you would just add a correction to bring you down into range. If you were consistently high at the next meal over a period of days then that might suggest that your basal insulin needed adjusting or that your ratio was wrong. You would look at the basal first and do a test by skipping lunch to see what happened in the absence of food and bolus insulin.
Just to give you an idea of the realities of diabetes and I am probably towards one extreme of the range, I often need 2 or 3 insulin corrections a day on top of my bolus for meals (although this is mostly for protein because I eat low carb) plus I need to adjust my Levemir (particularly my evening dose) on an almost daily basis sometimes. So last night I got a lovely flat line in the 5s with 2.5 units of Levemir, down from 3.5u the previous night. This afternoon for the second day in a row, I have been hedge cutting in my field and I will need to reduce it by another unit or perhaps1.5 units tonight. If I don't I will hypo. By contrast I need 22 units in the morning which is pretty consistent, unless I do lots of exercise on consecutive days and my basal dose is down to 0 at night and I am still hypoing overnight, so I have to start reducing the morning dose. When I am exercising less, the doses will go back up.
